CaMKIIδ Is Necessary for Endothelial Cell Migration and Regulates Spouting Angiogenesis through Modification of MEF2‐dependent Gene Expression

• Published in: The FASEB journal 2020-04, Vol.34 (S1), p.1-1
• Main Authors: O’Brien, Brendan J., Ginnan, Roman G., Singer, Harold A.
• Format: Article
• Language: English
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fasebj.2020.34.s1.03277

Abstract only Angiogenesis is a key homeostatic process of the endothelium that is essential for development and nourishment of hypoxic parenchyma. It is, however, also implicated as a contributor to a variety of pathologies such as rheumatoid arthritis, cancer metastasis, endometriosis, and multiple forms of retinopathy. Multifunctional Ca 2+ /Calmodulin–dependent protein kinase II (CaMKII) is a ubiquitous serine/threonine kinase with tissue‐specific expression and function. Data from our lab shows that CaMKII regulates VSM migration and proliferation in an isoform‐specific manner in the context of vascular remodeling following injury. We have also shown that CaMKII regulates gene expression downstream of MEF2, a key regulator of differentiation and angiogenesis, via phosphorylation of class II HDACs. Endothelial cell migration is a critical process that determines efficiency of vessel outgrowth and accurate directional commitment toward chemotactic and haptotactic cues. The goal of this study is the classify the CaMKII isoforms and their splice variants present in the endothelium and test their function in cell migration and angiogenesis. Knockdown of CaMKIIδ using RNAi attenuated both IL‐6 and VEGF‐dependent endothelial cell migration as measured by velocity and Euclidean distance in a single cell time lapse assay as well as a scratch wound. Additionally, in an electrode‐based quantitative wounding assay, cells treated with siCaMKIIδ healed standardized wounds significantly slower than non‐targeting siRNA controls. To investigate CaMKIIδ’s role in angiogenesis in vivo , we utilized the neonatal mouse retina as our model. Transgenic mice with an inducible VE‐Cadherin Cre were used to knock out CaMKIIδ and γ independently or simultaneously in an endothelial‐specific manner. In this model, we found that CaMKIIδ knockout animals have a 45% reduction of vascular outgrowth at postnatal day 6, fewer sprouts, and fewer anastomoses. These animals also display venous hypertrophy and delayed remodeling of the primary vascular plexus at postnatal day 10, consistent with a delayed angiogenic phenotype. Additionally, the knockout animals display hyperbranching, increased vessel coverage, and decreased lacunarity when allowed to grow to adulthood. The CaMKIIδ/γ double knockout phenocopies the δ knockout, suggesting that the observed phenotype is largely a δ effect. MEF2‐dependent gene expression in the endothelium was attenuated when CaMKIIδ was knocked down using siR